THE NATURAL MUTATION Y248C OF HUMAN ANGIOTENSINOGEN LEADS TO ABNORMALGLYCOSYLATION AND ALTERED IMMUNOLOGICAL RECOGNITION OF THE PROTEIN

Common molecular variants of the angiotensinogen gene have been associ ated with human hypertension, The rare Tyr to Cys change at residue 24 8 of mature angiotensinogen was identified in one pedigree, Heterozygo us individuals (Y248C) had a 40% decrease in plasma angiotensinogen co ncentration and a 35% reduction of the angiotensin I production rate, Recombinant wild-type (Tyr-248) and mutant (Cys-248) proteins were sta bly expressed in Chinese hamster ovary cells, Angiotensinogen monoclon al antibodies revealed marked differences in the epitope recognition o f the mutant protein and allowed the demonstration of its presence in plasma of Y248C individuals, Similar kinetic constants of angiotensin I production with human renin were observed for both proteins, Western blot analysis showed similar heterogeneities; however, a 3-kDa increa se in molecular mass for the Cys-248 protein was observed after immuno purification, Metabolic labeling of the intracellular Cys-248 protein showed a 61-kDa band in addition to the 55.5 and 58-kDa bands observed for the Tyr-248 protein, with all bands being sensitive to endoglycos idase H. In addition, pulse-chase studies revealed a slower intracellu lar processing for the Cys 248 protein, In conclusion, the Cys-248 mut ation alters the structure, glycosylation, and secretion of angiotensi nogen in Chinese hamster ovary cells and is accompanied by a decrease in plasma angiotensinogen concentration in Y248C individuals.